Optimizing insulin-to-carb ratios with Dr. Saleh Adi

Chief Medical Advisor and pediatric endocrinologist Dr. Saleh Adi discusses guidelines to help you optimize insulin-to-carb ratios with your patients. Drawing from his decades of expertise, he highlights example use cases and insulin-to-carb ratio optimization techniques, which you can also find in our webinars library.

Insulin-to-carb ratios in clinic care

Insulin-to-carb ratio (ICR), also known as carb ratio or carb factor, is a calculation used to determine how many grams of carbs are covered by one unit of rapid-acting insulin for a person with diabetes. Determining this ratio ensures that the patient’s glucose levels stay within the target range you have set with them.

Insulin-to-carb ratios often change in tandem with changes to the patient’s insulin sensitivity factor (ISF). Typically, ICR is a little more stable than ISF throughout adolescence and adulthood. Typically, ICR is calculated with an equation called the “Rule of 500,” wherein you divide the number 500 by the patient’s total daily dose of insulin (basal plus bolus). Dr. Adi finds that an ICR of 1:15 (one unit of insulin to 15 grams of carbohydrates) generally works for most adults and children as a starting point, but more insulin-resistant patients will typically require a more aggressive ICR (less than 1:15).

Ideally, Dr. Adi recommends reviewing insulin-to-carb ratios — along with other diabetes data — every six weeks in children and every few months in adults. This regular data analysis may seem to place additional pressure on your valuable time as a healthcare provider, but with Tidepool’s software and Dr. Adi’s recommendations, you can reclaim more time to focus on goal-setting conversations with your patients.

Optimizing insulin-to-carb ratios

Optimizing ICR is a step-by-step process that Dr. Adi says starts with first optimizing the patient’s basal rate and basal-to-bolus ratio. He explains that having a steady basal rate in the background better allows healthcare professionals to isolate the effect of the basal rate from the effect of any boluses the patient delivers. You may want to review our recent blog post on “Optimizing basal rates” for further information on this topic.

After optimizing basal rates, finding what Dr. Adi calls “pure events” is key for assessing and calculating insulin-to-carb ratios. Dr. Adi says the following four factors contribute and make up what he considers to be a pure event:

• A single insulin dose for a meal or correction.
• Preceded by a stable CGM (continuous glucose monitor) trace for at least one hour.
• Followed by no events — including carbs, corrections, or moderate to high intensity exercise — for three to four hours.
• A stable basal rate in the background.

To identify patterns and evaluate ICR settings, Dr. Adi recommends using the Daily View in Tidepool Web to see actionable information based on your patient’s insulin pump, blood glucose meter, and CGM data all in one place.

If you’re struggling to find a single event in the patient’s diabetes data, Dr. Adi says you can look at periods of time where multiple insulin doses were given but the other three pure event guidelines have been met. In this situation, look at the multiple insulin doses as a single event and analyze trends before and after.

Next, see if you can establish a pattern with three to four similar events over a maximum period of three weeks. If multiple insulin bolus doses keep recurring in those events and you can’t isolate a singular bolus, ask the patient to skip their morning snack or space out their meals for a few days.

“You have to pay attention to and address [core concepts]. When you’re doing calculations based on those numbers that you see on the pump, you have to know your patient. You’ve got to trust them.

You’ve got to say, ‘Okay, who’s counting the carbs? I can see that you didn’t estimate the carbs quite right for this meal and that’s why you ended up so high. Can you pay really close attention for the next three or four days and pre-weigh and pre-count everything before you put it on the table, so that you have food that’s already calculated? Because we’re going to have to rely on that for calculating the [insulin-to-carb ratios].'

Don’t feel bad about asking them to do something for you or some extra work for a couple days.”

At the end of the day, Dr. Adi says knowing and trusting your patients is going to go a long way towards helping you to optimize their ICR settings. When you and your patient work together, you can feel more confident that their day-to-day diabetes management has been made a little easier and that you’re getting all the relevant information you need to help them adjust their therapy settings, empowering both you and your patients to focus more on what matters.

Have any follow-up questions about insulin-to-carb ratio optimization? Check out our full “Helping your patients optimize ICR” webinar via our webinars library, or explore our other Tidepool for telemedicine videos on our YouTube page.